Vehicles with stop-start functionality provide reduction in fuel consumption. For an automatic transmission, during engine idle stop, the transmission pump stops as well and can no longer supply hydraulic oil pressure to the automatic transmission. When the engine re-starts after an idle stop, the transmission needs to be put in gear quickly in order to prevent vehicle launch delay. Using a conventional automatic transmission, during an engine restart after idle stop, the time required for the pump to energize the transmission, apply the gear, and make the transmission ready for vehicle launch is undesirably long.
U.S. Pat. No. 6,162,147 describes a hydraulic circuit for an automatic transmission operable to reduce time delay in shifting by using a source supplying pressurized fluid through a feed orifice and a charging circuit including an accumulator. Commonly owned U.S. patent application Ser. No. 13/162,888 filed Jun. 17, 2011 teaches use of a sliding spool to block openings and fluid flow in a clutch.